Reticular Connective Tissue: Reticular tissue Function, Fibers, Location and Histology

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Reticular Connective Tissue Definition

Reticular Connective Tissue is a type of loose connective tissue that is made up of a delicate 3-dimensional network of type III collagen that helps to support cells and other tissues.

What is Reticular Connective Tissue?

Reticular connective tissue is characterized by a cellular framework and does not run in bundles but rather as delicate and thin network of fibers and is mostly seen in lymphatic tissues and bone marrow.

Reticular Tissue Histology

Reticular tissue is stained specifically by silver impregnation; this renders them black and makes them easily distinguishable from type I collagen fibers that are stained brown. Due to the affinity of reticular fibers for silver salts, reticular fibers are sometimes called argentophil fibers this is probably due to the more carbohydrates contained in reticular fibers than Type I fibers.

Reticular connective tissue showing the reticular cells and reticular fibers
Reticular connective tissue showing the reticular cells and reticular fibers

 

Reticular Connective Tissue Structure

Reticular connective tissue does not gather into large bundles as in collagenous fibers but tend to form delicate networks. This type of loose connective tissue is not seen in routinely prepared sections but can be demonstrated with silver stains or by the periodic acid-Schiff (PAS) reagent this reagent reacts with proteoglycans that bind reticular unit fibrils together. When viewed with an electron microscope, the unit fibrils of reticular fibers show the same banding pattern as the unit fibrils of type I collagen fibers even though they are different in structure in terms of number, diameter, and pattern of arrangement of the unit fibrils.

Reticular Connective Tissue Function

Reticular tissue provides a very delicate meshwork that serves as a scaffold to other tissues and also supports other cells and tissues. This type of tissue is abundant in certain lymphoid organs where the reticular fibers form attachment sites for lymphocytes and other immune cells. The reticular tissue is an essential component in all basement membranes.

Reticular Cells

In the spleen, bone marrow and lymph nodes, the reticular fibers network is closely associated with reticular cells; most of these reticular cells are modified fibroblast while some are macrophages.

Reticular cells are stellate with processes that extend along reticular fibers in order to make contact with neighboring cells. The cytoplasm of these reticular cells stains lightly and is reduced or occupies a small space but their nuclei stain weakly. The reticular cells are responsible for the production and maintenance of the reticular fibers.

Reticular connective tissue seen under microscope (X200): This Micrograph shows a silver section of lymph node in which reticular fibers are seen as irregular black lines while the reticular cells are heavily stained dark.
Reticular connective tissue seen under microscope (X200): This Micrograph shows a silver section of lymph node in which reticular fibers are seen as irregular black lines while the reticular cells are heavily stained dark.

 

Reticular Fibers

Reticular fibers are short and thin fibers made of collagen type III fibrillar strands (reticular fibers were once described as a distinct variety of fibers, but are now regarded as one variety of collagen fibers). Reticular fibers are only visible under microscope by use of special stains.

Reticular fibers of type III collagen are produced and enveloped by the reticular cells, forming an elaborate network through which interstitial fluid or lymph and wandering cells from blood pass continuously. The reticular fibers show striations of about 67nm (they are very thin) and they differ from typical Type I collagen fibers because they are much finer, have uneven thickness and they form a network (or reticulum) by branching and by anastomosing with each other as reticular fibers do not run in bundles.

Where is Reticular Tissue Found?

Reticular tissue is found in abundantly in lymphoid tissues and glands and can be found scattered throughout other connective tissues. Reticular connective tissue is also found in relation to smooth muscles and nerve fibers.

Reticular Connective Tissue Location

  1. Lymph nodes
  2. Spleen
  3. Bone marrow
  4. Glands
  5. Kidneys

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